Bacterial Leaching of Copper Ores Several types of bacteria capable of living in an acid environment have been isolated from copper mine waters. The foremost of these are of the genus Thiobacillus (T.). Thiobacillus bacteria are acidophilic aerobic chemolithotrophs which grow most rapidly at a pH in the range of 2-3. T. ferrooxidans derive their … Read more
Here is a set carbon column that are obviously designed for the carbon in column process 4′ dia. X 11.5′ tall Columns 6′ dia. X 2′ deep upper tanks with 8″ dia. drain Columns offset by 2′ Platforms with railings and connecting stairs
When cyaniding a precious metal ore containing pyrrhotite, various compounds such as, thiosulphate, thiocyanate, ferrocyanide and soluble sulphide are formed and found in the cyanide solution. Soluble sulphides, if present at all, are found only in relatively small amounts; on the other hand thiosulphate, thiocyanate and ferrocyanide have been found in solutions in amounts of … Read more
Dissolution of Precious Metals in Sodium Zinc Cyanide: The dissolving effect of sodium zinc cyanide on precious metals has been the subject of much discussion. According to one researcher, pure K2Zn(CN)4 in the presence of oxygen dissolves gold with the formation of gold potassium cyanide and zinc oxide. Another researcher compared the dissolving effects of KCN and … Read more
Titration of Cyanide Solutions Containing Dissolved Zinc: Sodium zinc cyanide reacts with silver nitrate to precipitate zinc cyanide: Na2Zn(CN)4 + AgNO3 = Zn(CN)2 + NaAg(CN)2 + NaNO3 In the presence of an alkali, considerably more silver nitrate must be added to sodium zinc cyanide before a precipitate is formed. Many investigators have claimed that this … Read more
In cyanidation, zinc (the Merrill-Crowe Process) is practically the universal precipitant for precious metals dissolved in cyanide solutions although for specific reasons aluminium and charcoal have been used. During the reactions involved in precipitation, the greater part of the zinc dissolves in the cyanide solution and forms various cyanogen complexes such as sodium or calcium … Read more
When heat is applied to a cyanide solution containing metallic gold, two opposing factors affect the rate of dissolution. The increase in temperature would be expected to increase the activity of the solution and thus increase the rate of dissolution of gold. At the same time the amount of oxygen in the solution would decrease … Read more
The role pH has in affecting gold leaching rates by cyanide and the functions of calcium hydroxide in cyanidation are as follow: 1. For safety and to prevent loss of cyanide by hydrolysis. 2. To prevent loss of cyanide by the action of carbon dioxide in the air. 3. To decompose bicarbonates in mill water … Read more
In discussing the effect of oxygen on the gold dissolution, one can understand the use of oxygen or an oxidizing agent is essential for the dissolution of gold under normal conditions of cyanidation. Such oxidizing agents as sodium peroxide, potassium permanganate, bromine, chlorine have been used with more or less success in the past; but … Read more
